The Cisco AS5850 is a high-density, ISDN and modem WAN aggregation system that provides both digital and analog call termination. It is intended to be used in service provider dial point-of-presence (POP) or centralized enterprise dial environments. The gateway components include hybrid trunk and port-handling cards (both functions are handled by different components in the same slot), dedicated port-handling cards, dedicated trunk cards, route switch controllers, power entry modules, and a blower unit to cool the chassis. An optional 2400W AC power shelf is also available. The gateway is designed with environmental monitoring and reporting functions to help maintain normal system operation and resolve adverse environmental conditions prior to loss of operation. If conditions reach critical thresholds, the system shuts down to avoid equipment damage from excessive heat or electrical current. The Cisco AS5850 accepts AC-input power using a separate, self-contained AC-input power shelf, which converts AC-input power into DC output for use by the universal gateway. The AC-input power shelf is rack-mounted and has a safety cover that shields the electrical connections in the power shelf rear. The AC-input to DC-output connection supplies -48 VDC-output power to the PEMFs. Power flows through the filter module to the backplane, where it is distributed to the RSC and feature cards.